We have a company that is currently having 90% of their emails being rejected with the following error:
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<mail.corporatefloors.com #5.5.0 smtp;550-(mail.corporatefloors.com) [188.8.131.52]:43920 is currently not permitted>
Yesterday we switched over T1 providers and after the change over I made the updates to the firewall for all of the policies for Exchange, VPN, etc along with the changes on the DNS side. All of the email comes through fine now but when they send out emails to people outside the internal exchange network they are coming back rejected. I did a look up on the ip and it appears to not be on any blacklists.. Is there something I am missing on the Exchange side the would be causing this problem.